Hydraulic or pneumatic rams



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u A m M5 United States Patent Oiiee 2,83%@32 Patented June 17, 1958 HYDRAULIC R PNEUMATIC RAMS Lionel Arthur Reynolds, Bassetts Pole, Sutton Coldlield, England, assignor to Tangyes Limited, Smethwick, England, a British company Application October 16, 1956, Serial No. 616,205

3 Claims. (Cl. 121-46) This invention relates to improvements connected with tluid operated rams and is especially applicable to hydraulic jacks.

The invention has for its object to provide in a uid operated ram means for limiting the stroke of the ram within the associated cylinder such that consequent upon the ram reaching the end of its permitted lift or stroke any further iluid pumped into the cylinder is returned to the uid reservoir.

The invention consists of means for limiting the stroke of a uid pressure ram within a cylinder, said ram including a transverse passageway, a transversely disposed and spring loaded trigger accommodated in said passageway, valve means for eiecting the connection of the uid chamber of the cylinder to the transverse passageway, and the wall of the cylinder being formed internally with an annular groove and one or more ports in communication with said groove, the said trigger being adapted to engage within the groove to admit of the opening of the valve means at the limit of the permitted stroke of the ram whereby the iluid chamber is put into communication with the said ports.

A preferred embodiment of the invention will now be described as applied to a hydraulic jack, reference being made to the accompanying drawings in which:

Fig. l is a part sectional elevation illustrating the ram in its lowermost position within the cylinder of the jack, and

Fig. 2 is a part sectional elevation of the parts seen in Fig. l, the ram being shown at its uppermost position within the cylinder.

As seen in the drawings, the jack comprises a cylinder 3 which is closed at its lower end by a base 4, the cylindcr accommodating a ram 5 incorporating a peripheral seal 6 at its lower end. The base of the ram is formed with an aperture 5a which is tapped for the reception of a screw threaded valve housing 7. The aperture 5a communicates with a passageway 5c formed transversely in the ram by means of a port 5b and a ball valve 8 is urged into closing engagement with the mouth of the port 5b by means of a thrust spring 9 accommodated within the valve housing 7. A iuted plunger 10 is located within the port 5b and is supported at its lower end by the ball valvevS. The upper end of the plunger l() abuts against the underside of a horizontal trigger 11 which is pivotally mounted within a trigger guide 12 slidably accommodated Within the transverse passageway 5c, the trigger guide together with the trigger being urged outwardly by means of a helical thrust spring 13 located between the end of the trigger guide and a shoulder formed in the passageway 5c. The trigger 11 is formed 65 with an upwardly and outwardly inclined nose 11a which is adapted to engage with a similarly shaped annular recess 3a provided near the upper end of the bore of the cylinder 3, the wall of the cylinder being provided with a plurality of vents 3b communicating the annular recess 3a with the uid reservoir (not shown) surrounding the cylinder.

In operation, fluid is pumped into the cylinder 3 whereby the ram is raised until the nose 11a of the trigger 11 is traversed into register with the annular recess '3a by means of the thrust spring 13, and further movement of the ram causes the trigger to be rocked downwardly thereby moving the ball valve 8 oft its seating through the agency of the Huted plunger 10. Due to the opening of the ball valve 8, the uid is permitted to ilow through the valve housing 7, the ports 5b, along the passageway 5c, and through the vents 3b into the uid reservoir whereby a build up of fluid pressure within the cylinder is avoided. When the ram 5 descends within the cylinder 3, the trigger 11 is returned wholly Within thevpassageway 5c by virtue of the co-operation of the nose 11a of the trigger with the inclined face of the annular recess 3a, the ball valve 8 being simultaneously reseated by the thrust spring 9.

I claim:

l, In a fluid pressure ram having a cylinder with walls forming a uid chamber and a ram therein, means for limiting the stroke of the ram within the cylinder comprising a transverse passageway in said ram with a transversely spring loaded guide block slidably mounted in the passageway, a trigger pivotally mounted in said guide block, said walls of said cylinder being formed internally with an annular groove and one or more ports in communication with said groove, said trigger being arranged for rocking movement by engagement with the sides of said groove, and valve means having an operative connection with said trigger for effecting the communication of said uid chamber of said cylinder with said transverse passageway when said trigger is rocked to effect the opening of said valve means at the limit of the permitted stroke of said ram whereby connection is established between said duid chamber and said ports.

2. Means for limiting the stroke of a fluid pressure ram within a cylinder according to claim l, wherein said valve means comprises a ball valve wherein the ball is displaced from its seating through the agency of a iluted plunger disposed between said ball and the underside of the trigger.

3. Means for limiting `the stroke of a fluid pressure ram within a cylinder according to claim 2, wherein the trigger is provided with a V-shaped nose and wherein the annular groove in the wall of the cylinder is formed with an inclined face whereby the trigger is automatically displaced against its spring loading wholly within the transverse passageway in the ram during the return stroke of the ram.

References Cited in the le of this patent UNITED STATES PATENTS 1,720,434 Pedersen July 9, 1929 FOREIGN PATENTS 466,824 vFrance Mar. 14, 1914 

